Editing CAD/CAM’s cryptic post processor language is difficult at least and dangerous at worse.
G Code Conversion software from Kentech Inc. can take you beyond the post processor world and have you working and converting G code directly.

https://youtu.be/2C6LqScmDdY

Working with G code directly has many advantages ... get more details here :
https://kentechinc.com/kipware-conversion-software/